Rheostat.



PATENTED FEB. 28, 1905.

w. H. PGWELL. I RHEOSTAT. APPLIGATIOH FILED 0OT.84, 1904,

Q "inven 'uuuuuur 12am P w l UNITED STATES Patented February 28, 1900.

PATENT -OFFICE.

WILLIAM H. POWELL, ()F EAST ORANGE, NEW JERSEY. ASSIGNOR 'IO (BROOK Eli-H EELER CUM PA NY, PURATIUN OF NEW J ERSEY,

()F A Mll llil l, NEW JERSEY, A COR- RHEOSTAT.

SPECIFICATION forming part of Letters Patent N 0. 783,979, datedFebruary 28, 1905.- Application iiled'Octiiber 24, 1904. Serial No.229,739.

To a whom it Hill/Z] concern:

Be it known that 1, WILLIAM H. Pownnn, a citizen of the United States ofAmerica, and a resident of East Orange, county of Essex, and State ofNew Jersey, ,have invented certain new and useful Improvements inRheostats, of which the following is a specification.

This invention relates to the manner of arranging and combining theresistance-condoctor and contact-blocks and tlie manner of their supportto form a substantial compact and ellective rheostat of few parts andsimple construction. The-form illustrated is designed for hand operationand for use as 'a startingrheostat for electric motors, as theconstruction claimed is especially well adapted to this purpose, whereina considerable mass is requisite to absorb the heat generated upon theoperation of the rheostati but special provision for the radiation anddispersion of the heat is of little importance, owing to the fact thataconsidcrablo interval of time elapses between successive operations.

In the accompanying sheet of drawings, which form a part of thisapplication, Figure 1 is a side view of a rheostat embodying myinvention. Fig. 2 is a top view with the upper plate broken away. Fig. 3is a detail showing a form of connection between an intermediatecontact-bar and the resistancerihbon.

A conducting-ribbon A, which may he of thin copper, iron, lcrman silver,or other conducting material, is coated with any suitable insulatingmaterial. A mixture of whiting, glue, and bichronmteof potash has beenfound well adapted to this purpose, as it can he applied in liquid Form,hardeus in the light, and will withstand a reasonably-high temperature.()no end of the ribbon is riveted to a post or block Ii and is coiledaround this block in a flat coil or spiral, the post forming the centerof the spiral. This post formsoneof thcterminals ol' the rhrostat, onecud being thrcmled and "provided with a out I: for this purpose. Theother end of the post is the iinal contact on which the circuit isclosed.

'to each block is bared of insulation, so as to make electrical contactbetween the ribbon and block. As preferably constructcddioth theconducting-ribbon and the contact-blocks are much thinner in proportionthan it has been practicable toillustrate them in Fig. 2, and, as shownin Fig. 3, the connection between theribbon and contact-block isconvenientlv made by obliquely slitting the edges of the block andpassing the ribbon through the slits. The" outer contact-block D of theline of blocks to which the outer end of the coil of ribbon is attachedis thicker than the intermediate blocks, and the end at which contact ismade has a separate piece c screwed to the block, so that it can beconveniently renewed, since the circuit is broken at this block.

Tho spirally-coiled conducting-ribbon is placed on a slate slab E,forming the under slate of the rhcostat. The terminal, end of thecentral post projects through a hole in this slab, and the lowerends ofthe intermediate contact-blocks rest against the ab. A slate slab F,conveniently of the smile size,

hn mstho upper side or face of the rheostat,

and a curved slotfis cutthrongh this slab, the outline of the slot inthat part0! the slab which is broken away in Fig. 2 being indie ted bydotted lines. The contacting-ends of t N3 contact-blocks projectthroughthis slot, and the spaces between the projecting ends are filledwith insulation G. A movable contact-arm H is mounted above the frontslab of the rhoostat and has a movement parallel to the surface of therheostat and the facooi the inclosml resistance-coil and over theprojecting ends of the contact-blocks. It is pivoted to a pin 1, whichforms the other terminal of the rheostat. one end being threaded andprovided with a nut i for this purpose. This pin is supported by theslate slabs and eccentric to the axis of the spirally-coiled ribbon, sothat the contactin part of the arm can be moved over a pati across theconvolutions of the ribbon and contact with the projecting ends of thecontactblocks,which are placed between diflerentconvolutions of the i.bbon. The arm is returned to the open position in which it isillustrated by a spring l\' and rests against a buffer L. The contactingpart rests on a dead-block N, which is attached to the upper slate.

hen the rheostat is operated to close the circuit to a motor, the arm islirst moved into contact with the block 1) and the circuit isestablished from the terminal I through the arm, the block I), thecoiled resistance-ribbmi from the outer to the inner end of-the centralpart forming the terminal B. lontinued movement of the arm over theintermediate contact-blocks cuts out resistance in sections, the outercoils being first cut out and lastly the inner coils, the circuit beinglinally established from the tcrminall through the arm to the terminalB, and the arm is held in place by a holding-magnet P.

In order to avoid too great a surge of current at the moment ofoperation from any contact to the next, the included resistance which isthereby cut out should always be Within a certain percentage of theresistance remamlngmthc circuit. If,onthcotherhand, the steps are muchsmaller than is really required in any part, there will be an undue mul-To meet both condiof the spiral coil, to which the contact-blocks aredirectly connected.

What I claim as new, and desire to secure by Letters Patent of theUnited States, is-

1. In a rheostat, the combination ofa resistance element consisting of aspirally-coiled conducting-ribbon, a movable contact member adapted tobe moved above and parallel to the hat face of the spiral coil, andcontact-blocks disposed in the path of the movable contact memberandcontacting with ditl'erentconvolu tions of the ribbon, substantially asdescribed.

2. In a rheostat the combination of a resistance element consisting of aspirally-coiled condnoting-ribbon, a contact-arm adapted to be movedabove and parallel to the flat face of the spiral coil, andcontact-blocks disposed in the path of the contact-arm and contactingwith dilierent convolutions of the ribbon, substantially as described.

3. in a rheostat the combination oi a resistance element consisting of aspirally-coiled conducting-ribbon, a contact-arm adapted to be movedabove-and parallel to the flat face of the spiral coil and eccentricthereto, and contact-blocks disposed in the path of the contactarm andcontacting with the different convotions of the ribbon, substantially asdescribed.

4. In a rheostat,the combination of rheostat terminals, a resistanceelement consisting of a coiled conducting-ribbon connected at the innerend of the coil to one of the terminals, a movable contact memberadapted to be moved above and parallel to the liat face of the spiralcoil. contact-blocks disposed in the path of the movable contact memberand contacting with the different convolutions of the ribbon, andconnections through the movable contact member to the other terminal,substantially as described.

Signed by me at East Orange, New Jersey, this 522d day of October.190-il \VILLI A M H.. POWELL. \Vitnesses:

SAMUEL W. Baton, Enwrn It. DoUoLAs.

